Journal of Orthopaedic Association of South Indian States

: 2022  |  Volume : 19  |  Issue : 1  |  Page : 29--32

A rare case of transient anisocoria following microlumbar discectomy: A case report and literature review

Rizwan Sait1, R Krishnakumar2,  
1 Department of Neurosurgery, Medical Trust Hospital, Kochi, Kerala, India
2 Department of Spine Surgery, Medical Trust Hospital, Kochi, Kerala, India

Correspondence Address:
Rizwan Sait
Department of Neurosurgery, Medical Trust Hospital, M. G. Road, Kochi - 682 016, Kerala


Ocular complications following surgeries in prone positions are rarely reported. With this case report, we present a 39-year-old female who developed transient anisocoria following microlumbar discectomy. Further evaluation showed mild uniocular third nerve palsy, which resolved spontaneously. By understanding the pathophysiology of this complication, we can avoid unnecessary investigations and costs.

How to cite this article:
Sait R, Krishnakumar R. A rare case of transient anisocoria following microlumbar discectomy: A case report and literature review.J Orthop Assoc South Indian States 2022;19:29-32

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Sait R, Krishnakumar R. A rare case of transient anisocoria following microlumbar discectomy: A case report and literature review. J Orthop Assoc South Indian States [serial online] 2022 [cited 2022 Sep 28 ];19:29-32
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Corneal and scleral injuries are the most common ophthalmological injuries following surgeries in prone position.[1] Postoperative loss of vision after surgery in prone position was reported with a prevalence of 0.028%–0.2%.[2] However, the third cranial nerve palsy associated with anisocoria is rarely reported. To the best of authors knowledge, only 3 such cases have been reported (Gupta et al., 2019; Papaioannou et al., 2019; and Singh 2021). We share our experience in this regard because spine surgeons and anesthesiologists should be aware of these potential ocular complications and need to take adequate precautions to avoid such devastating events. By knowing the differential diagnosis, we can avoid unnecessary investigations and costs.

 Case Report

A 39-year-old female patient presented with complaints of low back pain with right lower limb radiculopathy for the last 1 year. There was no history of subjective weakness or paresthesia. Sensory, bladder, and bowel functions were found to be intact. She was evaluated with magnetic resonance imaging (MRI) lumbosacral spine, which was suggestive of the right paracentral disc bulge at the level of L5-S1. Initially managed conservatively with oral medications. But as her pain continued to worsen and could no longer be alleviated by oral analgesics, decided to proceed with discectomy.

After doing necessary preanesthetic workup and obtaining requisite consents, the patient was shifted to the operating room, routine monitors were attached, and anesthesia was induced with propofol (titrating doses) and fentanyl 2 mcg/kg. Endotracheal intubation was done with cuffed flexo-metallic tube sized 7.5 mm. Foley's catheterization was done. The patient was positioned carefully in the prone position with padding of all the pressure points and free the abdomen. The head was placed on head positioner (Disposa-View) at the heart level with avoidance of pressure on the eyes. All pressure points were meticulously padded. The patient underwent L5-S1 microdiscectomy. Surgery lasted for 2 h and less than 50 ml of blood loss occurred. Intraoperatively, she was transfused with 1000 ml of crystalloids. After the surgery, the patient was kept back in supine position and reversed with 2.5 mg neostigmine and 0.5 mg glycopyrrolate, extubated, and shifted to the intensive care unit (ICU) for observation. At no point was atropine given to the patient.

Postoperatively, the patient became conscious and alert and her radiculopathy was immediately subsided with minimal surgical site pain. No periorbital edema or facial puffiness was noticed. Pupillary examination revealed mild anisocoria. Her right pupil was 2 mm briskly reacting and left pupil was 2.5 mm briskly reacting. Her bedside ophthalmological examination did not show any decrease in visual acuity or restricted extraocular movements or field defects. The patient did not complain of any diplopia or blurring of vision in the immediate postoperative. As the patient remained neurologically stable, she was shifted out of ICU 4 h after surgery. Later by evening, the patient was reassessed and noted that pupillary asymmetry was persisting and the patient started complaining of mild binocular diplopia with near vision when using mobile phone. She did not have any symptoms and signs of raised intracranial pressure.

Ophthalmology consultation sought and was thoroughly evaluated. Her fundus examination was normal and slit-lamp examination did not show any iris muscle tear. She was diagnosed with left eye mild oculomotor nerve palsy. In view of isolated unilateral third nerve palsy, suspecting acute cerebral vascular events, she was evaluated with MRI brain screening and MR cerebral and neck vessel angiogram. MRI did not show any features of diffusion restriction, vascular occlusion, or anomalies. Anisocoria improved spontaneously within 48 h of stay, and as her diplopia resolved, she was discharged on the third postoperative day. The patient had no visual complaints or evidence of anisocoria during her follow-up visits.

 Review of literature

To the best of our knowledge, only 3 similar cases of anisocoria following posterior spine surgery have been published [Table 1].{Table 1}

Gupta et al., 2019, reported the case of a 48-year-old male patient developed unilateral mydriasis associated with diplopia and blurred vision following a L4-L5, L5-S1 microdiscectomy. Parasympathetic postganglionic nerve injury causing segmental pupillary palsy was considered to be the probable cause of anisocoria. Corrective lenses were used, and the patient was discharged on the 11th postoperative day with mild anisocoria.[1]

Papaioannou et al., 2019, reported the case of a 23-year-old female patient developed transient anisocoria following a L1-S2 fixation, L5 decompression, and Ilizarov application for calcaneal fracture. 24 h after surgery, anisocoria resolved. Iris sphincter muscle tear was the probable cause of anisocoria.[3]

Singh, 2021, reported the case of a 71-year-old female patient developed transient anisocoria following a D11-L3 bilateral pedicle screw fixation and L1 laminectomy. Anisocoria improved spontaneously within 48 h and the patient discharged on 6th postoperative day. Transient oculomotor paralysis was the probable cause for anisocoria.[4]


Pupillary muscles are innervated by the autonomic nervous system. Sympathetic nerve fibers supply dilator pupillae via superior cervical ganglion, which enters the eye through long ciliary nerves of the first division of trigeminal nerve. Parasympathetic nerve fibers supply sphincter pupillae via Edinger–Westphal nucleus near oculomotor nerve and enter the eye through short ciliary nerves.[1]

New-onset anisocoria following a surgery in prone position requires a thorough ophthalmological evaluation to differentiate ocular versus central causes. In more than 90% of cases, faulty positioning causing prolonged compression on globe results in parasympathetic postganglionic nerve injury and produces pupillary asymmetry. Sometimes, frequent adjustments in operating table for getting better fluoroscopic images can cause displacement of head rest and can cause globe compression.

Another important cause which needs to take into consideration is exposure to pharmaceutical agents such as lidocaine hydrochloride, epinephrine, and ipratropium bromide, which can cause mydriasis. Diagnosis of pharmacologically dilated pupil depends on the diagnosis of ptosis and extraocular movement abnormalities with normal-appearing iris and lack of constriction of pupil following 1% topical pilocarpine administration.[3]

It is rare in an alert patient with an isolated anisocoria with out extraocular movement restriction or ptosis to develop a third cranial nerve palsy due to a central cause. It is better for the treating surgeon and anesthetist to have an understanding regarding other related causes of isolated third nerve palsy, which includes ipsilateral brain herniation (Hutchinson pupil) or a posterior communicating artery aneurysm.

The transient anisocoria developed in our case might be due to accidental slippage of head from silicon base causing compression of left eye and parasympathetic denervation or due to pharmacological effect of locally instilled bupivacaine 0.5% over surgical site to reduce the post op pain.[5]


For spine surgeries in prone position, both surgeon and anesthetist should be aware of the ophthalmological complications and need to take precautions as recommended by the American Society of Anesthesiologists [Table 2].[6] Although rare, patients should be counseled regarding ocular complications before obtaining consent for surgery.{Table 2}

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.


1Gupta P, Adabala VB, Barik AK. Unilateral mydriasis: A complication of spine surgery in prone position. Braz J Anesthesiol 2019;69:319-21.
2Newman NJ. Perioperative visual loss after nonocular surgeries. Am J Ophthalmol 2008;145:604-10.
3Papaioannou I, Xristopoulos K, Baikousis A, Korovessis P, Kokkinis K. Anisocoria after posterior spine surgery: A rare but disastrous complication – A case report and literature review. J Orthop Case Rep 2019;9:92-5.
4Singh H. Transient anisocoria following spine surgery in the prone position: A case report. IAR J Med Case Rep 2021;2:16-8.
5Arun BG, Puttaswamygowda C, Kulkarni A. Transient isolated unilateral oculomotor nerve palsy following accidental dural puncture after bilateral total knee replacement. Indian J Anaesth 2019;63:75-6.
6American Society of Anesthesiologists Task Force on Perioperative Visual Loss. Practice advisory for perioperative visual loss associated with spine surgery: An updated report by the American society of anesthesiologists task force on perioperative visual loss. Anesthesiology 2012;116:274-85.